A semiconductor integrated circuit including a MOS transistor is known to malfunction if damaged by an Electrostatic Discharge (ESD).
As an ESD model of the semiconductor integrated circuit, following three types are present:
(1) Human Body Model (HBM): human body charging model
(2) Machine Model (MM): machine model
(3) Charged Device Model (CDM): device charging model
The HBM and the MM are models with respect to ESD damage caused by an object charged with a static electricity from the outside. The CDM is a model with respect to ESD damage when the semiconductor integrated circuit itself is charged and discharges to a metal contact.
During microfabrication and operation of a semiconductor integrated circuit, an ESD countermeasure is typically applied, and ESD protection circuits have been developed for these uses. However, since it is preferred that a chip area and a size of the ESD protection circuit be reduced, and the possible ESD discharge pathways are complicated, it is difficult to provide ESD resistance to a semiconductor device.